Static exposure experiments were conducted to assess the toxicity of dispersed Prudhoe Bay Crude Oil (PBCO) to embryos of the topsmelt (Atherinops affinis). Treatment with the dispersant COREXIT 9500 resulted in greater hydrocarbon concentrations in chemically enhanced water-accommodated fractions (CEWAFs) of oil, relative to the untreated water-accommodated fractions (WAFs). Topsmelt embryo development and survival to hatching was significantly inhibited in CEWAF tests while minimal effects on embryo-larval survival were observed in WAF tests. Increased hydrocarbon concentrations in the CEWAF tests caused cardiovascular and other abnormalities in developing topsmelt embryos.